Abbey yesterday agreed the sale of train-leasing company Porterbrook for a reported £2bn amid concerns that the bank's owner, Banco Santander of Spain, had joined the list of major financial institutions wounded by the credit crunch.

Abbey said the business, which provides rolling stock for rail franchises, was no longer "core" to its ambitions as a high street bank and its sale to a consortium of Deutsche Bank, Lloyds TSB and BNP Paribas would allow the bank to focus on retail customers. The sale came as analysts began to question the finances of Santander, which until now was considered among the most robust of all the big European banks.

Analysts at broker Keefe, Bruyette & Woods said Santander was coming under pressure to boost its finances after a deterioration in its home market and its main overseas markets in Latin America. "We now see an increasing risk of earnings downgrades, a deteriorating risk profile and growing pressure to strengthen its capital."

An Abbey spokeswoman denied that it had been a forced sale. "The reasoning behind selling Porterbrook is that it is not core to our retail banking business," she insisted.

Porterbrook is one of Britain's largest train-leasing businesses. It owns 6,064 carriages it leases to operators including Southern and South West Trains - two of the biggest commuter franchises.

The train-leasing business has recently been dominated by large banking groups.

Angel Trains was owned by Royal Bank of Scotland, which sold the company in June to a consortium led by Babcock & Brown, an Australian investment firm. RBS sold the business in order to bolster its balance sheet after a £12bn share issue but the bank was overwhelmed months later by further turmoil in the financial markets and was forced to accept a government bail-out.

HSBC owns the remaining significant player in the train-leasing market, HSBC Rail, but has appointed NM Rothschild to explore options for the business, including a disposal.

HSBC, along with Santander, was considered to have escaped the worst of the credit crunch until recently, but its operations in the far east have come under strain since the credit crunch spread to Asia this autumn.

Abbey was largely unaffected while its business in Spain and Latin America remained robust. However, Latin American markets have begun to panic as concerns have spread that their economies could suffer a wide-ranging and deep recession.

The rail-leasing firms were born out of the Major government's privatisation of British Rail in the mid-1990s. Porterbrook was sold in 1996 to buy-out firm Charterhouse Capital Partners, which turned an investment of £73.6m into £825m when it sold the firm in August of that year to Stagecoach.

A parliamentary watchdog criticised the sale. It said the Treasury was short-changed by £900m from the sale of the leasing companies. Abbey bought the firm in 2000 for £1.4bn.

Porterbrook dismissed fears that the sale, plus the recent £3.6bn deal for Angel Trains, will delay plans to add 1,300 rail carriages to the British network by 2014.

"The consortium has looked at this business in the context of future investment in rolling stock and I believe that they want to develop it along those lines," said Paul Francis, Porterbrook's managing director. The Department for Transport, which is commissioning the new carriages, said it was "confident" that the ownership changes would not affect its carriage programme.

The future of the train-leasing industry was thrown into doubt last year when the Competition Commission was asked to investigate the market. Angel Trains said the inquiry could derail the government carriage programme. However, the commission has indicated that it will not punish the train lessors and has instead found that the way the government sets out franchises is a bigger restriction on competition.